1. Field of the Invention
The present invention relates to a method of realizing machining results of a given workpiece, and more particularly a method of realizing machining results from visual recognition of the difference between the pre-machining state and the post-machining state of a given workpiece.
2. Related Arts
FIG. 4 shows how a semiconductor wafer W to be diced is like. As shown, it has a lattice pattern formed thereon, defining a plurality of squares by crossing streets S. The semiconductor wafer is cut into small squares or chips from which integrated circuits can be fabricated.
Some chips may be contaminated with debris, which is the remains of semiconductor material broken to minute pieces when the semiconductor wafer is being cut. The so contaminated chips must be rejected as being of poor quality. Therefore, microscopic examination is required to make a decision as to whether or not each semiconductor wafer has grooves free of such debris or whether or not it is contaminated elsewhere with debris.
From microscopic photographs, however, minute pieces of remains are hardly distinguishable from portions of micro-circuit patterns formed on small squares in the semiconductor wafer. This is the cause for a wrong decision on the permissibility of chips.
The same trouble may be caused in machining other than the dicing of semiconductor wafers.
There has been, therefore, an ever increasing demand for realizing the post-machining state of a given workpiece with accuracy.
One object of the present invention is to provide a method of realizing the post-machining state of a given workpiece with accuracy.
To attain this object a method of realizing machining results of a given workpiece according to the present invention comprises the steps of: obtaining an image of a selected area in the workpiece with picture-taking means before a required machining is performed on the workpiece; obtaining an image of the selected area in the workpiece with picture-taking means after the required machining has been performed on the workpiece; making a comparison between the image prior to the required machining and the image post of the required machining to derive non-common portions from the comparison; and realizing how the machined portion or portions in the selected area are like.
The workpiece may be a semiconductor wafer; the required machining may be the dicing of the semiconductor wafer; the selected area may be streets on which cutting is effected to separate the semiconductor wafer into small squares or dice; and state of grooves in the semiconductor wafer resulted by cutting is realized.
The workpiece may be a semiconductor wafer; the required machining may be the dicing of the semiconductor wafer; the selected area may be in the semiconductor wafer; and state of contaminant scattered and attached on the semiconductor wafer is realized.
Only the portions of the workpiece which are changed as a result of machining are left for inspection by removing the portions which remain unchanged in the workpiece, thus permitting one to make a correct determination on the post-machining state of the workpiece. In dicing a semiconductor wafer one can have a clear image of each groove shape and width and of minute particles of semiconductor material broken from the semiconductor wafer.
Other objects and advantages of the present invention will be understood from the following description of the manner in which the machining results of a given semiconductor wafer can be realized according to the present invention, which manner is illustrated in accompanying drawings.